A patient's spinal column includes twenty-six bones called vertebrae which protect the spinal cord. While the shape and/or size of each vertebra varies depending on the placement, loading, posture, and/or pathology within the spinal column, each vertebra is composed of cancellous bone, which is a spongy type of osseous tissue. The cancellous bone of each vertebra is then covered by a thin coating of cortical bone, which is a hard and dense type of osseous tissue. An intervertebral disc is positioned between each pair of adjacent vertebrae in the spinal column. Each disc forms a fibrocartilaginous joint between adjacent vertebrae so as to allow movement of the vertebrae. Beyond enabling relative motion between adjacent vertebrae, each disc acts as a shock absorber for the spinal column.
Each disc comprises a fibrous exterior surrounding an inner gel-like center, which together cooperate to distribute pressure evenly across each disc, which prevents the development of stress concentrations that might otherwise damage and/or impair the vertebrae of the spinal column. However, the discs may be subject to various injuries and/or disorders which may interfere with the disc's ability to adequately distribute pressure and protect the vertebrae. For example, disc herniation, degeneration, and infection may result in insufficient disc thickness and/or support to absorb and/or distribute forces imparted to the spinal column. Disc degeneration, for example, may result when the inner gel-like center begins to dehydrate, which may result in a degenerated disc having decreased thickness. This decreased thickness may limit the ability of the degenerated disc to absorb shock which, if left untreated, may result in pain and/or vertebral injury.
While pain medication, physical therapy, and other non-operative conditions may alleviate some symptoms, such interventions may not be sufficient for every patient. Accordingly, various procedures have been developed to surgically improve patient quality of life via abatement of pain and/or discomfort. One particularly advantageous procedure includes transforaminal lumbar interbody fusion (TLIF). TLIF may be performed via a minimally invasive technique, thus reducing trauma to the spinal column, and decreasing patient recovery times.
During TLIF, a medical professional may make a small (e.g., between about 1 inch and about 6 inches) incision along a patient's back. Next, one or more portions of the vertebral bone (such as, e.g., a facet joint of adjacent vertebral bodies) may be removed so as to access a disc between adjacent vertebrae. A medical professional then may partially remove the damaged and/or degenerated disc, leaving at least a portion of the disc intact to facilitate guiding an interbody device into the disc space. If necessary, bone graft (including, but not limited to, morselized bone) also may be placed within the disc space to promote fusion. Commonly, a medical professional may enlarge the disc space between adjacent vertebrae via a distraction process. Following removal of a portion of the disc and/or distraction of the disc space, an interbody device (e.g., implant) is positioned in the disc space between adjacent vertebrae. The interbody device may relieve pressure from pinched nerves and provide additional therapeutic effects. In some instances, a medical professional also may implant one or more bone screws and/or rods to provide additional support to the spinal column. Additionally, morselized bone may be placed along the sides of the spinal column to promote fusion.
When a TLIF procedure is performed according to a minimally invasive technique, however, direct vision of the disc space is not available. In addition, it may be difficult to visualize an interbody device during implantation. Accordingly, proper placement of an interbody device along the spinal column may be a difficult and tedious task, often requiring extensive skill and experience. Additionally, it is often the case that the available space (e.g., distance) between two adjacent vertebrae intended to receive an interbody device is smaller than the height of the interbody device chosen for insertion. In such cases, a medical professional may need to distract the disc space to prepare for insertion of the interbody device. Distraction, however, is often done with various tools and implements (e.g., rods, screws, etc.) which may interfere, impede, and/or block an interbody device's insertion and/or entrance into the disc space. Accordingly, it may be difficult to guide the interbody device into position between adjacent vertebrae that have been distracted by conventional methods. If distraction is not performed, however, it may be challenging to insert the interbody device so as to create sufficient space between (e.g., distract) adjacent vertebrae itself, while maintaining control. Further, during insertion of the interbody device, the interbody device may impact remaining portions of the disc and/or bone graft which may interfere with the proper placement of the interbody device.
Thus, there remains a need for improved interbody devices, associated systems, tools, and insertion methods.